Bisdithiophosphoric acid derivatives as lubricant additives

ABSTRACT

There are disclosed compounds of formula I                    
     wherein 
     R 1  and R 2  are each independently of the other C 3 -C 18 alkyl, C 5 -C 12 cycloalkyl, C 5 -C 6 cycloalkylmethyl, C 9 -C 10 bicycloalkylmethyl, C 9 -C 10 tricycloalkylmethyl, phenyl, 
     C 7 -C 24 alkylphenyl or, taken together, are                    
     R 3  is C 2 -C 18 alkylene which is interrupted by —O—, —S—, or —NR 4 —, or is a group of formula                    
     R 4  is hydrogen, C 1 -C 18 alkyl, phenyl-C 1 -C 4 alkyl, phenyl or C 1 -C 6 alkyl-substituted phenyl, 
     R 5  is hydrogen or methyl. 
     These compounds are particularly suitable for use as additives for lubricant compositions, hydraulic fluids and machining fluids.

This application is a continuation, of application Ser. No. 08/068,377,filed May 27, 1993 now abandoned.

The present invention relates to novel bisdithiophosphoric acidderivatives, to the use thereof as additives in lubricants, machiningfluids and hydraulic fluids, and to compositions containing saidderivatives.

Mixed oxothiophosphoric acids are disclosed as, lubricant additives inU.S. Pat. No. 4,544,492.

Methyl esters of formula

R′₂ are hydrocarbon radicals and R′₃ is hydrogen or lower alkyl, aredisclosed for the same utility in GB 1 347 845.

Dithiophosphoric acid derivatives which contain —C═C— double bonds or—C(OH)— groups are disclosed in U.S. Pat. No. 4,081.387.

Adducts of dithiophosphoric acids and acrylates are disclosed in U.S.Pat. No. 3,784,588. These adducts are esters of monohydric to hexahydricalcohols. The use of such compounds in hydraulic oils is disclosed in EP465 156.

Surprisingly, it has been found that some esters of dihydric alcoholshave particularly good properties as lubricant additives.

Specifically, the invention relates to compounds of formula

wherein

R₁ and R₂ are each independently of the other C₃-C₁₈alkyl,C₅-C₁₂cycloalkyl,

C₅-C₆cycloalkylmethyl, C₉-C₁₀bicycloalkylmethyl,C₉-C₁₀tricycloalkylmethyl, phenyl,

C₇-C₂₄alkylphenyl or, taken together, are

R₃ is CH₂_(b), C₄-C₄₀alkylene which is interrupted by —O—, —S—, or—NR₄—, or is a group of formula

R₄ is hydrogen, C₁-C₁₈alkyl, phenyl-C₁-C₄alkyl, phenyl orC₁-C₆alkyl-substituted phenyl,

R₅ is hydrogen or methyl, and

b is an integer from 3 to 18.

Preferred compounds of formula I are those wherein R₁ and R₂ are eachindependently of the other C₃-C₁₀alkyl, C₅-C₆cycloalkyl,C₅-C₆cycloalkylmethyl, C₉-C₁₀bicycloalkylmethyl,C₉-C₁₀tricycloalkylmethyl, phenyl, C₇-C₁₈alkylphenyl or, taken together,are

R₃ is CH₂_(b), C₄-C₂₀alkylene which is interrupted by —O— or NR₄, oris a group of formula

R₄ is hydrogen or C₁-C₄alkyl, and b is an integer from 3 to 10, andcompounds wherein R₅ is hydrogen.

Also preferred are compounds wherein R₃ is CH₂_(b), C₄-C₁₂alkylenewhich is interrupted by —O— or NR₄, or is

R₄ is C₁-C₄alkyl and b is an integer from 3 to 6.

Further preferred compounds are those wherein R₁ and R₂ are C₃-C₆alkyl.

b is preferably 4 to 6 and, most preferably, 4.

R₄ is preferably hydrogen or C₁-C₄alkyl.

R₁ and R₂ defined in the above formulae as C₃-C₁₈alkyl are branched orunbranched radicals. Illustrative examples are propyl, isopropyl,n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl,3-heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, 2-ethylbutyl,1-methylpentyl, 1,3-dimethylbutyl, 1,1,3,3-tetramethylbutyl,1-methylhexyl, isoheptyl, 1-methylheptyl, 1,1,3-trimethylhexyl or1-methylundecyl.

R₁ and R₂ defined as C₅-C₁₂cycloalkyl may typically be cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl or cyclododecyl. Cyclopentyl andcyclohexyl are preferred. Cyclohexyl is most preferred.

R₁ and R₂ defined as C₅-C₆cycloalkylmethyl will be taken to meancyclopentylmethyl and, preferably, cyclohexylmethyl.

R₁ and R₂ defined as C₉-C₁₀bicycloalkylmethyl are typicallydecalinylmethyl. R₁ and R₂ defined as C₉-C₁₀tricycloalkylmethyl arepreferably a group of formula

R₁ and R₂ defined as C₉-C₂₄alkylphenyl are phenyl groups which aresubstituted by one or more than one alkyl group, preferably by 1 to 3,most preferably 1 or 2, alkyl groups together containing 3 to 18 carbonatoms. Typical examples of such alkyl groups are methyl and ethyl andthose cited above.

R₁ and R₂ are preferably identical.

Interrupted C₄-C₄₀alkylene R₃ is preferably straight-chain andpreferably contains ethylene units with alternating O, S or NR₄. Theinterruption is preferably by oxygen, resulting in polyethylene glycolgroups.

The invention further relates to compositions comprising

a) a lubricant, a machining fluid or hydraulic fluid, and

b) at least one compound of formula I as described above.

Preferred compositions are those wherein R₁ and R₂ are eachindependently of the other C₃-C₁₀alkyl, C₅-C₆-Cycloalkyl,C₅-C₆cycloalkylmethyl, C₉-C₁₀bicycloalkylmethyl,C₉-C₁₀tricycloalkylmethyl, phenyl, C₇-C₁₈alkylphenyl or, taken together,are

R₃ is CH₂_(b), C₄-C₂₀alkylene which is interrupted by —O— or NR₄, oris a group of formula

R₄ is hydrogen or C₁-C₄alkyl and b is an integer from 3 to 10.

Particularly preferred compositions are those wherein

R₃ is CH₂_(b), C₄-C₁₂alkylene which is interrupted by —O— or NR₄, oris

R₄ is C₁-C₄alkyl and b is an integer from 3 to 6, and also compositionswherein R₅ is hydrogen.

Compositions meriting special interest are those wherein R₁ and R₂ areC₃-C₆alkyl.

The lubricants, machining fluids or hydraulic fluids contained in theinventive compositions can decompose readily to a greater or lesserdegree under the action of heat, mechanical stress (especially inducedby shear forces) and chemical reagents (especially atmospheric oxygen).

The compounds of formula I afford protection against such influences andwill conveniently be present in the novel compositions in amounts of0.01 to 10% by weight, typically 0.05 to 5% by weight, preferably 0.05to 3% by weight and, most preferably, 0.1 to 2% by weight. The novelcompositions may contain one or more than one of these compounds, andthe percentages by weight are based on the total amount of saidcompounds. The basis of calculation is the total weight of thelubricant, machining fluid or hydraulic fluid without the compounds offormula I.

The invention thus also relates to the use of compounds of formula I asadditives for lubricants, hydraulic fluids and machining fluids,especially as extreme-pressure and antiwear additives as well asfriction modifiers.

Such a utility also entails a process for enhancing the performanceproperties of lubricants, hydraulic fluids and machining fluids. Thenovel utility also encompasses the protection of the metal parts to belubricated against mechanical wear (antiwear protection).

The suitable lubricants, hydraulic fluids and machining fluids aretypically based on mineral or synthetic oils or mixtures thereof. Thelubricants are known to the skilled person and are described in therelevant literature, inter alia in Dieter Klamann, “Schmier-stoffe andverwandte Produkte” (Lubricants and Related Products) (Verlag Chemie,Weinheim, 1982), in Schewe-Kobek, “Das Schmiermittel-Taschenbuch”(Handbook of Lubricants) (Dr. Alfred Hüthig-Verlag, Heidelberg, 1974),and in “Ullmanns Enzyklopädie der technischen Chemie” (Ullmann'sEncyclopedia of Industrial Chemistry), Vol. 13, pages 85-94 (VerlagChemie, Weinheim, 1977).

The lubricants are preferably oils and fats are typically derived from amineral oil. Oils are preferred.

A further group of lubricants suitable for use in the practice of thisinvention comprises vegetable or animal oils, fats, tallows and waxes ormixtures with one another or with the mineral or synthetic oils referredto above. Vegetable and animal oils, fats, tallows and waxes aretypically palm nut oil, palm oil, olive oil, beet oil, rapeseed oil,linseed oil, ground nut oil, soybean oil, cottonseed oil, sunflower seedoil, pumpkin seed oil, coconut oil, corn oil, castor oil, walnut oil andmixtures thereof, fish oils, the tallows of slaughter animals, e.g. beeftallow, neat's foot and bone oil, as well as the modified, epoxidisedand sulfoxidised forms thereof, typically epoxidised soybean oil.

The mineral oils are based in particular on hydrocarbon compounds.

Synthetic lubricants typically comprise lubricants based on aliphatic oraromatic carboxylates, polymeric esters, polyalkylene oxides,phosphates, poly-α-olefins or silicones, on a diester of a divalent acidwith a monohydric alcohol, typically dioctyl sebacate or dinonyladipate, on a triester of trimethylolpropane with a monovalent acid orwith a mixture of acids, conveniently trimethylolpropane tripelargonate,trimethylol-propane tricaprylate or mixtures thereof, on a tetraester ofpentaerythritol with a monovalent acid or with a mixture of such acids,typically pentaerythritol tetracaprylate, or on a complex ester ofmonovalent and divalent acids with polyhydric alcohols, for example acomplex ester of trimethylolpropane with caprylic and sebacic acid or ofa mixture thereof. Especially suitable lubricants are, in addition tomineral oils, typically poly-α-olefins, ester-based lubricants,phosphates, glycols, polyglycols and polyalkylene glycols and mixturesthereof with water.

Machining fluids and hydraulic fluids can be prepared from the samesubstances as those described above in connection with the lubricants.Often they are also emulsions of such substances in water or otherliquids.

The lubricating compositions of this invention are used, inter alia, forcombustion engines, typically for motor vehicles powered by engines ofthe Otto-cycle, diesel, two-stroke, Wankel or orbital type.

The compounds of formula I are readily soluble in lubricants, machiningfluids and hydraulic fluids and are therefore especially suitable foruse as additives for lubricants, machining fluids and hydraulic fluids.Their surprisingly good antiwear properties merit special mention.

The invention thus further relates to a process for enhancing theperformance properties of lubricants, machining fluids and hydraulicfluids, which comprises adding thereto compounds of formula I.

The compounds of formula I can be blended with the lubricatingcompositions in a manner known per se. The compounds are, for example,readily soluble in oils. It is also possible to prepare a masterbatch,which can be diluted in accordance with consumption to suitableconcentrations with the appropriate lubricant. In such cases,concentrations higher than 10% by weight are also possible.

The lubricants, machining fluids and hydraulic fluids of this inventionmay also contain other additives which are added for further enhancementof the basic properties. These further additives comprise antioxidants,metal deactivators, rust inhibitors, viscosity improvers, pour-pointdepressants, dispersants, detergents, other extreme-pressure andantiwear additives.

Illustrative examples of such further additives are:

EXAMPLES OF PHENOLIC ANTIOXIDANTS

1. Alkylated monophenols, for example 2,6-di-tert-butyl-4-methylphenol,2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol,2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol,2,6-dicyclopentyl-4-methylphenol,2-(α-methylcyclo-hexyl)-4,6-dimethylphenol,2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol,2,6-di-tert-butyl-4-methoxymethylphenol, 2,6-dinonyl-4-methylphenol,2,4-dimethyl-6-(1′-methylundec-1′-yl)phenol,2,4-dimethyl-6-(1′-methylheptadec-1′-yl)phenol,2,4-di-methyl-6-(1′-methyltridec-1′-yl)phenol and mixtures thereof.

2. Alkylthiomethylphenols, for example2,4-dioctylthiomethyl-6-tert-butylphenol,2,4-di-octylthiomethyl-6-methylphenol,2,4-dioctylthiomethyl-6-ethylphenol and2,6-didodecyl-thiomethyl-4-nonylphenol.

3. Hydroquinones and alkylated hydroquinones, for example2,6-di-tert-butyl-4-methoxy-phenol, 2,5-di-tert-butylhydroquinone,2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4-octa-decyloxyphenol,2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole,3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenylstearate and bis-(3,5-di-tert-butyl-4-hydroxyphenyl) adipate.

4. Hydroxylated thiodiphenyl ethers, for example2,2′-thiobis(6-tert-butyl-4-methylphenol), 2,2′-thiobis(4-octylphenol),4,4′-thiobis(6-tert-butyl-3-methylphenol),4,4′-thiobis-(6-tert-butyl-2-methylphenol),4,4′-thiobis(3,6-di-sec-amylphenol) and4,4′-bis-(2,6-di-methyl-4-hydroxyphenyl) disulfide.

5. Alkylidene bisphenols, for example2,2′-methylenebis(6-tert-butyl-4-methylphenol),2,2′-methylenebis(6-tert-butyl-4-ethylphenol),2,2′-methylenebis[4-methyl-6-(α-methyl-cyclohexyl)phenol],2,2′-methylenebis(4-methyl-6-cyclohexylphenol),2,2′-methylenebis-(6-nonyl-4-methylphenol),2,2′-methylenebis(4,6-di-tert-butylphenol),2,2′-ethylidenebis-(4,6-di-tert-butylphenol),2,2′-ethylidenebis(6-tert-butyl-4-isobutylphenol),2,2′-methylenebis[6-(α-methylbenzyl)nonylphenol],2,2′-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol],4,4′-methylenebis(2,6-di-tert-butylphenol),4,4′-methylenebis(6-tert-butyl-2-methylphenol),1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane,ethylene glycol bis[3,3-bis-(3′-tert-butyl-4′-hydroxyphenyl)butyrate],bis(3-tert-butyl-4-hydroxy-5-methylphenyl)dicyclopentadiene,bis[2-(3′-tert-butyl-2′hydroxy-5′-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate,1,1-bis(3,5-dimethyl-2-hydroxyphenyl)butane,2,2-bis(3,5-di-tert-butyl-4hydroxyphenyl)propane,2,2-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercaptobutaneand 1,1,5,5-tetra(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane.

6. O-, N- and S-Benzyl compounds, for example3,5,3′,5′-tetra-tert-butyl-4,4′-dihydroxydi-benzyl ether, octadecyl4-hydroxy-3,5-dimethylbenzyl-mercaptoacetate,tris(3,5-di-tert-butyl-4-hydroxybenzyl)amine,bis(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-dithio-terephthalate,bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide and isooctyl3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate.

7. Hydroxybenzylated malonates, for example dioctadecyl2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)malonate, dioctadecyl2(3-tert-butyl-4-hydroxy-5-methylbenzyl)malonate, didodecylmercaptoethyl2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate andbis[4-(1,1,3,3-tetramethylbutyl)phenyl]2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate.

8. Aromatic hydroxybenzyl compounds, for example1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene,1,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetramethylbenzeneand 2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol.

9. Triazine compounds, for example2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazine,2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazine,2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,3,5-triazine,2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,2,3-triazine,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate,1,3,5-tris(4-tert-butyl-3-hydroxy-2,6dimethylbenzyl) iso-cyanurate,2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine,1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexahydro-1,3,5-triazineand 1,3,5-tris(3,5-di-cyclohexyl-4-hydroxybenzyl) isocyanurate.

10. Benzylphosphonates, for example dimethyl2,5-di-tert-butyl-4-hydroxybenzylphosphonate, diethyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate, dioctadecyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate, dioctadecyl5-tert-butyl-4-hydroxy-3-methylbenzylphosphonate and the calcium salt ofmonoethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate.

11. Acylaminophenols, for example 4-hydroxylauranilide,4-hydroxystearanilide and octylN-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate.

12. Esters of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid withmono- or polyhydric alcohols, for example with methanol, ethanol,octadecanol, 1,6-hexanediol, 1,9-no-nanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, di-ethyleneglycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide, 3-thiaundecanol,3-thiapentadecanol, trimethylhexanediol, tri-methylolpropane and4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo-[2.2.2]octane.

13. Esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acidwith mono- or polyhydric alcohols, for example with methanol, ethanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N′-bis-(hydroxyethyl)oxamide, 3-thiaundecanol,3-thiapentadecanol, trimethylhexanediol, trimethylolpropane and4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo-[2.2.2]octane.

14. Esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid withmono- or polyhydric alcohols, for example with methanol, ethanol,octadecanol, 1,6-hexanediol, 1,9-no-nanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, di-ethyleneglycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N′-bis-(hydroxyethyl)oxamide, 3-thiaundecanol,3-thiapentadecanol, trimethylhexanediol, tri-methylolpropane and4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo-[2.2.2]-octane.

15. Esters of 3,5-di-tert-butyl4hydroxyphenylacetic acid with mono- orpolyhydric alcohols, for example with methanol, ethanol, octadecanol,1,6-hexanediol, 1,9-nonane-diol, ethylene glycol, 1,2-propanediol,neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethyleneglycol, pentaerythritol, tris(hydroxyethyl) isocyanurate,N,N′-bis-(hydroxyethyl)oxamide, 3-thiaundecanol, 3-thiapentadecanol,trimethylhexanediol, trimethylolpropane and4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.

16. Amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, forexampleN,N′-bis-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hexamethylenediamine,N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)trimethylenediamineand N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine.

Examples of Aminic Antioxidants

N,N′-diisopropyl-p-phenylenediamine,N,N′-di-sec-butyl-p-phenylenediamine,NN′-bis-(1,4-dimethylpentyl)-p-phenylenediamine,N,N′-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine,N,N′-bis(1-methylheptyl)-p-phenylenediamine,N,N′-dicyclohexyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine,N,N′-bis(2-naphthyl)-p-phenylenediamine,N-isopropyl-N′-phenyl-p-phenylenediamine,N-(1,3-dimethyl-butyl)-N′-phenyl-p-phenylenediamine,N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine,N-cyclohexyl-N′-phenyl-p-phenylenediamine,4-(p-toluenesulfamoyl)diphenylamine,N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine,N-alkyldiphenylamine, 4-isopro-poxydiphenylamine,N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, octylateddi-phenylamine, for example p,p′-di-tert-octyldiphenylamine,4-n-butylaminophenol, 4-buty-rylaminophenol, 4-nonanoylaminophenol,4-dodecanoylaminophenol, 4-octadecanoyl-aminophenol,bis(4-methoxyphenyl)amine,2,6-di-tert-butyl-4-dimethylaminomethyl-phenol,2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,N,N,N′,N′-tetra-methyl-4,4′-diaminodiphenylmethane,1,2-bis[(2-methyl-phenyl)amino]ethane, 1,2-bis-(phenylamino)propane,(o-tolyl)biguanide, bis[4-(1′,3′dimethylbutyl)phenyl]amine,tert-octylated N-phenyl-1-naphthylamine, a mixture of mono anddialkylated tert-butyl/tert-octyldiphenylamines, a mixture of mono- anddialkylated isopropyl/isohexyldiphenyl-amines, mixtures of mono- anddialkylated tert-butyldiphenylamines,2,3-dihydro-3,3-di-methyl-4H-1,4-benzothiazine, phenothiazine,N-alkylphenothiazine, N,N,N′,N′-tetra-phenyl-1,4-diaminobut-2-one,N,N-bis(2,2,6,6-tetramethylpiperid-4-yl-hexamethylenedi-amine,bis(2,2,6,6-tetramethylpiperid-4-yl) sebacate,2,2,6,6-tetramethylpiperidin-4-one and2,2,6,6-tetramethylpiperidin-4-ol.

Examples of other Antioxidants

Aliphatic or aromatic phosphites, esters of thiodipropionic acid or ofthiodiacetic acid, or salts of dithiocarbamic or dithiophosphoric acid,2,2,12,12-tetramethyl-5,9-dihydroxy-3,7,1 1-trithiatridecane and2,2,15,15-tetramethyl-5,12-dihydroxy-3,7,10,14-tetrathiahexa-decane.

Examples of Metal Deactivators, for Example for Copper, are

a) Benzotriazoles and derivatives thereof, for example 4- or5-alkylbenzotriazoles (e.g. tolutriazole) and derivatives thereof,4,5,6;7-tetrahydrobenzotriazole and 5,5′-methylenebisbenzotriazole;Mannich bases of benzotriazole or tolutriazole, e.g.1-[bis(2-ethylhexyl)aminomethyl)tolutriazole and1-[bis(2-ethylhexyl)amino-methyl)benzotriazole; andalloxyalkylbenzotdazoles such as 1-(nonyloxymethyl)-benzotriazole,1-(1-butoxyethyl)benzotriazole and1-(1-cyclohexyloxybutyl)-tolutriazole.

b) 1,2,4-Triazoles and derivatives thereof, for example 3-alkyl(oraryl)-1,2,4triazoles, and Mannich bases of 1,2,4-triazoles, such as1-[bis(2-ethylhexyl)aminomethyl-1,2,4-triazole;alkoxyalkyl-1,2,4-triazoles such as 1-(1-butoxyethyl)-1,2,4-triazole;and acylated 3-amino-1,2,4-triazoles.

c) Imidazole derivatives, for example4,4′-methylenebis(2-undecyl-5-methylimidazole) andbis[(N-methyl)imidazol-2-yl]carbinol octyl ether.

d) Sulfur-containing heterocyclic compounds, for example2-mercaptobenzothiazole, 2,5-dimercapto-1,3,4-thiadiazole andderivatives thereof; and3,5-bis[di(2-ethyl-hexyl)aminomethyl]-1,3,4-thiadiazolin-2-one.

e) Amino compounds, for example salicylidenepropylenediamine,salicylaminoguanidine and salts thereof.

Examples of Rust Inhibitors are

a) Organic acids, their esters, metal salts, amine salts and anhydrides,for example alkyl- and alkenylsuccinic acids and their partial esterswith alcohols, diols or hydroxycarboxylic acids, partial amides ofalkyl- and alkenylsuccinic acids, 4-nonylphenoxyacetic acid, alkoxy- andalkoxyethoxycarboxylic acids such as dode-cyloxyacetic acid,dodecyloxy(ethoxy)acetic acid and the amine salts thereof, and alsoN-oleoylsarcosine, sorbitan monooleate, lead naphthenate,alkenylsuccinic anhydrides, for example dodecenylsuccinic anhydride,2-(carboxyethyl)-1-dodecyl-3-methylglycerol and the amine salts thereof.

b) Nitrogen-containing compounds, for example:

I. Primary, secondary or tertiary aliphatic or cycloaliphatic amines andamine salts of organic and inorganic acids, for example oil-solublealkylammonium carboxylates, and also1-[N,N-bis(2-hydroxyethyl)amino]-3-(4-nonyl-phenoxy)propan-2-ol.

II. Heterocyclic compounds, for example: substituted imidazolines andoxazo-lines, and 2-heptadecenyl-1-(2-hydroxyethyl)imidazoline.

c) Phosphorus-containing compounds, for example: Amine salts ofphosphoric acid partial esters or phosphonic acid partial esters, andzinc dialkyldithiophosphates.

d) Sulfur-containing compounds, for example: bariumdinonylnaphthalenesulfonates, calcium petroleum sulfonates,alkylthio-substituted aliphatic carboxylic acids, esters of aliphatic2-sulfocarboxylic acids and salts thereof.

e) Glycerol derivatives, for example: glycerol monooleate,1-(alkylphenoxy)-3-(2-hydroxyethyl)glycerols,1-(alkylphenoxy)-3-(2,3-dihydroxypropyl)glycerols and2-carboxyalkyl-1,3-dialkylglycerols.

Examples of Viscosity Index Improvers are

Polyacrylates, polymethacrylates, vinylpyrrolidone/methacrylatecopolymers, polyvinylpyrrolidones, polybutenes, olefin copolymers,styrene/acrylate copolymers and polyethers.

Examples of Pour-point Depressants are

Polymethacrylate and alkylated naphthalene derivatives.

Examples of Dispersants/surfactants are

Polybutenylsuccinic amides or -imides, polybutenylphosphonic acidderivatives and basic magnesium, calcium and barium sulfonates andphenolates.

Examples of Antiwear Additives are

Sulfur- and/or phosphorus- and/or halogen-containing compounds, e.g.sulfurised olefins and vegetable oils, zinc dialkyldithiophosphates,alkylated triphenyl phosphates, tritolyl phosphate, tricresyl phosphate,chlorinated paraffins, alkyl and aryl di- and trisulfides, amine saltsof mono- and dialkyl phosphates, amine salts of methylphosphonic acid,di-ethanolaminomethyltolyltriazole,bis(2-ethylhexyl)aminomethyltolyltriazole, derivatives of2,5-dimercapto-1,3,4-thiadiazole, ethyl3-[(diisopropoxyphosphinothioyl)thio]propionate, triphenyl thiophosphate(triphenylphosphorothioate), tris(alkylphenyl) phosphoro-thioate andmixtures thereof (for example tris(isononylphenyl) phosphorothioate),di-phenyl monononylphenyl phosphorothioate, isobutylphenyl diphenylphosphorothioate, the dodecylamine salt of 3-hydroxy-1,3-thiaphosphetane3-oxide, trithiophosphoric acid 5,5,5-tris[isooctyl 2-acetate],derivatives of 2-mercaptobenzothiazole such as1-[N,N-bis-(2-ethylhexyl)aminomethyl]-2-mercapto-1H-1,3-benzothiazole,and ethoxycarbonyl-5-octyldithiocarbamate.

The compounds of this invention are prepared by methods which are knownper se, conveniently in accordance with the following scheme:

Addition of the dithiophosphoric acid II to acrylic or methacrylic acidIII gives the carboxylic acid IV, which is esterified by conventionalmethods, typically by adding p-toluenesulfonic acid as catalyst, with adialcohol V to give the desired bis-compound VI. The synthesis can becarried out in general accordance with the process described in GB 1 347845.

Specific parameters for carrying out the process embraced by the abovereaction scheme can be inferred from the following working Examples.These Examples and the Use Examples illustrate the invention in moredetail, but without implying any restriction thereto. Unless otherwiseindicated, parts and percentages are by weight.

Example 1 O,O-Diisoamyl-S-2-carboxyethyl Dithiophosphate

With stirring, 23.44 g (0.33 mol) of acrylic acid are added at 70° C.over 1 hour to 93.24 g (0.3 mol) of diisoamyl dithiophosphate and themixture is then stirred for 4 hours at 75° C. The readily volatileconstituents are removed under vacuum (70° C./0.08 mbar/2 h). The liquidis clarified by filtration by addition of a filter aid. Yield: 108.3 g(93%) of a pale yellow liquid, n_(D) ²⁰: 1.4983, ³¹p-NMR: 94.9ppm/H₃PO₄.

Example 2 Bis-3′-(O,O-diisoamyldithiophosphoryl)propionyl-1,4-butanediol

70.98 g (0.21 mol) of the dithiophosphate prepared according to Example1, 9.01 g (0.1 mol) of 1,4-butanediol, 0.57 g of p-toluenesulfonic acidand 100 ml of toluene are refluxed for c. 3 h on a water separator untilthe water of reaction has been completely removed.

The resultant product is then washed with 60 ml of a 10% solution ofsodium sulfate and twice with 60 ml of a 10% solution of sodiumsulfate/5% solution of sodium carbonate and dried over anhydrous sodiumsulfate. The solvent is subsequently removed by distillation on a rotaryevaporator and residual solvent is stripped off under vacuum (60 C./0.05mbar/2 h).

Yield: 73.6 g (99%) of a yellow liquid, n_(D) ²⁰: 1.5008, ³¹P-NMR: 94.7pptn/H₃PO₄.

The compounds of Examples 3 to 11 listed in Table 1 are prepared ingeneral accordance with the procedure described in Example 2.

TABLE 1 [(RO)₂P(S)—S—CH₂—CH₂—CO—O]₂R ® Example R ® R Yield (%) n_(D) ²⁰³¹P-NMR ppm/H₃PO₄  3 CH₃N(CH₂CH₂—)₂ i-propyl 71 1.5075 91.3  4O[CH₂—CH(CH₃)—]₂ i-Propyl 96 1.5005 91.4  5 O(CH₂CH₂—O—CH₂CH₂—)₂ ^(≠))i-propyl 87 1.5031 91.2  6 O(CH₂CH₂—O—CH₂CH₂—O—CH₂CH₂—)₂*⁾ i-propyl 851.4997 91.2  7

i-propyl 96 1.5226 91.5  8 (—CH₂—)₄ i-butyl 96 1.5036 91.5  9 (—CH₂—)₄n-propyl 97 1.5136 94.9 10 (—CH₂)₄ i-propyl 97 1.5087 91.1 11 (—CH₂—)₆i-propyl 96 1.5057 91.5 ^(≠))Average number of ethylene groups: 4, basedon polyethylene glycol 200 as dihydric alcohol *⁾average number ofethylene groups 6, based on polyethylene glycol 300 as dihydric alcohol

Example 12 SRV Test

To test the antiwear and friction reducing properties, the noveldithiophosphates are incorporated in an undoped lubricating oil and thecoefficient of friction μ is determined at 100° C. and 150° C. using theSRV apparatus (oscillating friction device supplied by Optimol GmbH,Munich; q.v. Lubrication Engineering 39 (11) 1982, Advert. Index cover3, page 729).

In this method, an oscillating ball (50 Hz) is pressed with a force of200 N against a firmly clamped metal cylinder on which there is a filmof test oil. The horizontal and vertical forces are measured with apiezoelectrical transducer. The signal so obtained is transmitted directto the recorder. At the conclusion of the test, the cross-section of thewear scar on the metal cylinder is measured with a profilometer(TALYSURF 10). The test results are summarised in Table 4.

TABLE 2 Wear Additive* [mm²10⁻⁵]^(≠) Coefficient of friction μ ExampleNo. 100° C. 150° C. 100° C. 150° C. — 85.2 217.4 0.121 0.122 4 25.5 41.50.093 0.075 7 18.5 53.5 0.097 0.080 8 20.5 35.5 0.104 0.081 9 25.0 40.00.096 0.075 *Additive concentration 2% in mineral oil, viscosity 139.3mm²s⁻¹ at 40° C. ^(≠)Cross-section of wear scar on the cylinder

The low wear index and coefficient of friction relative to the undopedbase oil demonstrate that the compounds have antiwear properties.

What is claimed is:
 1. A compound of the formula

wherein R₁, R₂, R₃ and R₄ independently of one another representC₃-C₁₈alkyl, C₅-C₁₂cycloalkyl, C₅-C₆cycloalkylmethyl,C₉-C₁₀bicycloalkylmethyl, C₉-C₁₀tricycloalkylmethyl, phenyl,C₇-C₂₄alkylphenyl or, taken together, are


2. A compound according to claim 1 wherein R₁, R₂, R₃ and R₄independently of one another represent C₃-C₆alkyl.
 3. A compoundaccording to claim 2 wherein R₁, R₂, R₃ and R₄ are identical.
 4. Thecompound

according to claim
 3. 5. A composition comprising a) a lubricant, amachining fluid or hydraulic fluid, and b) at least one compoundaccording to claim
 1. 6. A composition comprising a) a lubricant, amachining fluid or hydraulic fluid, and b) at least one compoundaccording to claim
 2. 7. A composition comprising a) a lubricant, amachining fluid or hydraulic fluid, and b) at least one compoundaccording to claim
 4. 8. A composition according to claim 5 whereincomponent a) is a lubricant.
 9. A composition according to claim 8wherein the lubricant is an engine oil.
 10. A process for enhancing theperformance properties of lubricant compositions, hydraulic fluids andmachining fluids, which comprises adding thereto at least one compoundaccording to claim
 1. 11. A process for enhancing the performanceproperties of lubricant compositions, hydraulic fluids and machiningfluids, which comprises adding thereto at least one compound accordingto claim
 2. 12. A process for enhancing the performance properties oflubricant compositions, hydraulic fluids and machining fluids, whichcomprises adding thereto at least one compound according to claim 4.